Krista Myer, a 43-year-old marathoner from Columbia, Missouri, had accepted that she would never be able to meet the Boston Marathon’s rigorous qualifying times. But after last year’s bombings, she wanted to be part of the race in whatever way she could.

So she applied to be a volunteer, writing to race organizers that she would “do absolutely anything that you need.”

Myer knew the odds were long, and didn’t get her hopes up. Still, when the rejection letter came came late last month, it stung.

“It’s just hit me that the Boston Marathon is so elusive, so elite, that I will likely not ever be chosen to even VOLUNTEER,” she wrote on her blog.

Spurred by the same sense of solidarity and resolve, legions of runners, volunteers, and spectators have felt drawn to take part in this year’s Marathon, compelled to participate in the race’s triumphant return, to be counted in a city’s defiant tribute.

From runners prevented from finishing last year’s race to volunteers willing to help in the smallest of ways, the vast interest has created a race of new scope, with a sharply expanded field of runners and volunteers, and crowds expected to top 1 million, twice the usual size.

‘We have such a dedicated group [of volunteers] that comes back year after year. It is very challenging for a brand new volunteer to be selected.’

“I feel even more honored to be a part of it this year,” said Alice Cuchetti, who has helped man the water station at the 13-mile mark for the past several years. “There’s a sense of pride. We want to be part of something bigger than us.”

Facing unprecedented demand, the Boston Athletic Association added spots for 9,000 more runners, then was inundated with more than 25,000 runner applications in just two weeks. Of some 5,600 runners who were invited back after being unable to finish last year’s race, about 5,000 will return.

Tom Grilk, the BAA’s executive director, said the “display of resilience and determination” that emerged after the bombing has carried forward, reinforcing the public’s connection to the race.

“It was an attack on Boston,” he said. “There’s an emotional component this year that is different. It leaves all of us with a sense of responsibility.”

The day after last year’s Marathon, in a swirl of anger and grief over the fatal bombings, Bob Andy made a vow. Next April, he told his wife, he was going to run the race himself.

It was a fine idea, she replied. There was just one problem. He didn’t run.

But Andy, 42, felt he had to try.

“All I kept thinking is that it could have been me, standing there with my kids,” he said. “I wanted to do something. I wanted to make a difference, somehow.”

Kate Laliberte, 38, will be running her first marathon, raising money for the Dana-Farber Cancer Institute. A breast cancer survivor, she started running two years ago, and after the bombings the idea of running Boston took hold. If she was ever going to run a marathon, this was the one.

She began training last summer, even though she didn’t have a number. She wanted to see if she could handle the distance, if the opportunity came. When it did, she ramped up her training, logging long runs in bitter cold.

Through the miles, she was motivated by a sense of defiance.

“You don’t want to be told you can’t do something,” she said.

Like the runners, volunteers have felt drawn to the momentous event, with more than 4,000 applying for a post on the first day that volunteer applications were accepted. Many say they feel a solidarity with the runners, the race, and the city itself, that the bombings have only made stronger.

Organizers set out to recruit 10,000 volunteers, 1,500 more than last year. But when registration opened in December, it quickly became clear they would clear that hurdle with ease.

“I always felt we would have more support than we could handle,” said Elisabeth Worthing, volunteer program manager for the Boston Athletic Association. “We have such a dedicated group that comes back year after year.”

With a record number of volunteers choosing to return, openings for newcomers were rare. Even as organizers welcomed the wave of interest from people wanting to support the runners and the city, they regretted having to turn nearly 5,000 applicants away.

“It is very challenging for a brand new volunteer to be selected,” Worthing said. “It’s heartbreaking in a way.”

John Santoro, a board member for a local Red Cross chapter, also found himself on the outside looking in. An emergency physician, Santoro figured organizers might need volunteers with medical expertise. But by the time he contacted them, the spots were filled.

Santoro said he was disappointed he won’t be participating on Marathon Monday, but said he was heartened by the outpouring of support.

“It speaks very well for the Boston community,” he said.

The Red Cross, which staffs medical stations along the Marathon course, saw nearly all of its volunteers from last year return, leaving few openings.

“They are passionate about what they do,” said Stephanie Walsh, who is overseeing some 380 Red Cross volunteers. “They don’t do it because it’s in vogue. They do it because they really want to help people.”

Cuchetti, 70, the water stop volunteer from Manchester, N.H., spent Saturday mornings this winter passing out Gatorade to runners training for Boston and raising money for the American Liver Foundation, including her husband. She’s gotten to know other runners, too, and has come to admire their determination to train through even the harshest conditions. Watching them run Boston, taking back their beloved race, will be deeply moving, she said.

“I can’t imagine there won’t be a lot of tears, a lot of joy,” she said. “Together we are strong.”

Soon after vowing to run Boston, Bob Andy began to train. In the fall, he applied to a half-dozen charities to get a bib, but struck out. In December, he saw a news story about the One Fund Boston Marathon team, and decided it was worth one last shot. A few weeks later, he had his number, and he was on his way.

“It’s very surreal this is happening to me,” he said. “Never in my dreams did I think I could do this. But this marathon is going to be amazing.”